Impact of interfacial dipole on effective work function of nickel fully silicided gate electrodes formed on rare-earth-based dielectric interlayers

Abstract

The mechanism underlying the modulation of nickel fully silicided (Ni-FUSI) gate work function m by rare-earth (RE)-based dielectric interlayers (RE: Y, Er, Dy, Tb, Yb, and La) was investigated. RE-O-Si bonding in these ultrathin (∼1 nm) interlayers induces highly polarized RE-O bonds at the gate/dielectric interface. The relative magnitude of the RE-O dipole was estimated from the product of the net electronegativity difference and the charge separation between the RE and O ions. Excellent correlation of the modulated Ni-FUSI m with the calculated dipole moment was shown. The proposed quantitative interfacial dipole model could be used for the selection of interlayer materials for further m optimization and precise control of threshold voltage in transistors. © 2007 American Institute of Physics.